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Add Custom Az/El target and drift scan plot to Star Tracker.

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This commit is contained in:
Jon Beniston
2021-05-24 12:34:38 +01:00
parent e9e96e2bec
commit b5339b1ec8
19 changed files with 843 additions and 383 deletions
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sdrbase/util/astronomy.cpp
+53 -27
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@@ -216,6 +216,47 @@ AzAlt Astronomy::raDecToAzAlt(RADec rd, double latitude, double longitude, QDate
return aa;
}
// Convert from altitude and azimuth, for location (decimal degrees) and time, to Jnow right ascension (decimal hours) and declination (decimal degrees)
// See: http://jonvoisey.net/blog/2018/07/data-converting-alt-az-to-ra-dec-example/
RADec Astronomy::azAltToRaDec(AzAlt aa, double latitude, double longitude, QDateTime dt)
{
RADec rd;
double lst_deg; // Local sidereal time
double ha_rad, ha_deg; // Hour angle
double alt_rad, az_rad, lat_rad, dec_rad; // Corresponding variables as radians
// Calculate local mean sidereal time (LMST) in degrees (see raDecToAzAlt)
lst_deg = Astronomy::localSiderealTime(dt, longitude);
// Convert degrees to radians
alt_rad = Units::degreesToRadians(aa.alt);
az_rad = Units::degreesToRadians(aa.az);
lat_rad = Units::degreesToRadians(latitude);
// Calculate declination
dec_rad = asin(sin(lat_rad)*sin(alt_rad)+cos(lat_rad)*cos(alt_rad)*cos(az_rad));
// Calculate hour angle
double quotient = (sin(alt_rad)-sin(lat_rad)*sin(dec_rad))/(cos(lat_rad)*cos(dec_rad));
// At extreme altitudes, we seem to get small numerical errors that causes values to be out of range, so clip to [-1,1]
if (quotient < -1.0) {
ha_rad = acos(-1.0);
} else if (quotient > 1.0) {
ha_rad = acos(1.0);
} else {
ha_rad = acos(quotient);
}
// Convert radians to degrees
rd.dec = Units::radiansToDegrees(dec_rad);
ha_deg = Units::radiansToDegrees(ha_rad);
// Calculate right ascension in decimal hours
rd.ra = modulo((lst_deg - ha_deg) / (360.0/24.0), 24.0);
return rd;
}
// Needs to work for negative a
double Astronomy::modulo(double a, double b)
{
@@ -493,10 +534,11 @@ double Astronomy::lstAndRAToLongitude(double lst, double raHours)
}
// Return right ascension and declination of North Galactic Pole in J2000 Epoch
// http://www.lsc-group.phys.uwm.edu/lal/lsd/node1777.html
void Astronomy::northGalacticPoleJ2000(double& ra, double& dec)
{
ra = 12 + 51.4 / 60.0;
dec = 27.13;
ra = 192.8594813/15.0;
dec = 27.1282511;
}
// Convert from equatorial to Galactic coordinates, J2000 Epoch
@@ -511,40 +553,24 @@ void Astronomy::equatorialToGalactic(double ra, double dec, double& l, double& b
const double ngpRaRad = Units::degreesToRadians(ngpRa * 15.0);
const double ngpDecRad = Units::degreesToRadians(ngpDec);
// Calculate galactic latitude for North Celestial pole, J2000
const double ncpLRad = Units::degreesToRadians(122.93192);
// Calculate galactic longitude in radians
double bRad = asin(sin(ngpDecRad)*sin(decRad)+cos(ngpDecRad)*cos(decRad)*cos(raRad - ngpRaRad));
// Find the two possible solutions for galactic longitude in radians
double rhs1 = cos(decRad)*sin(raRad-ngpRaRad)/cos(bRad);
double rhs2 = (-cos(decRad)*sin(ngpDecRad)*cos(raRad-ngpRaRad)+sin(decRad)*cos(ngpDecRad))/cos(bRad);
double l1 = ncpLRad - asin(rhs1);
double l2 = ncpLRad - acos(rhs2);
// Calculate galactic latitiude in radians
double lRad = atan2(sin(decRad)-sin(bRad)*sin(ngpDecRad), cos(decRad)*cos(ngpDecRad)*sin(raRad - ngpRaRad));
// Plug them back in and select solution which is valid for both equations
// (Error should be 0, but we have to allow for small numerical differences)
// There's probably a better way to solve this.
double l1lhs1 = sin(ncpLRad - l1);
double l1lhs2 = cos(ncpLRad - l1);
double l2lhs1 = sin(ncpLRad - l2);
double l2lhs2 = cos(ncpLRad - l2);
double l1Diff = abs(l1lhs1 - rhs1) + abs(l1lhs2 - rhs2);
double l2Diff = abs(l2lhs1 - rhs1) + abs(l2lhs2 - rhs2);
double lRad;
if (l1Diff < l2Diff)
lRad = l1;
else
lRad = l2;
// Ascending node of the galactic plane in degrees
double lAscend = 33.0;
// Convert to degrees in range -90,90 and 0,360
b = Units::radiansToDegrees(bRad);
l = Units::radiansToDegrees(lRad);
if (l < 0.0)
l = Units::radiansToDegrees(lRad) + lAscend;
if (l < 0.0) {
l += 360.0;
if (l > 360.0)
}
if (l > 360.0) {
l -= 360.0;
}
}
// The following functions are from Starlink Positional Astronomy Library